Introduction: Annular injury is commonly used to induce lumbar intervertebral disc degeneration in pre-clinical animals studies. We present a detailed radiological analysis of the changes, which occur in a three level ovine model of disc degeneration, and correlate this with biochemical changes.
Methods: 6 sheep underwent annular incisions (6mm by 20mm) performed at L2/3, L3/4 and L4/5 via a left lateral retroperitoneal approach. Adjacent lumbar discs were not operated and served as controls. X-rays were obtained prior to injury and 3 months post injury. 3T MR imaging was performed at 3 months post sacrifice and analysed using the Pfirrmann Disc Degeneration Scoring system. Discs underwent biochemical analysis to determine proteoglycan content within the AF and NP, as well as DNA content.
Results: Injured discs (n=18) demonstrated a significant reduction in DHI of 0.02318 (95% CI 0.018 to 0.028, P<0.0001), corresponding to a 23.67% mean decrease in DHI over the three-month period, whilst non-injured discs (n=12) demonstrated no significant difference in DHI. Median Pfirrmann disc degeneration scores for the non-injured and injured groups were 1 and 2 respectively, and the difference between the two groups was significant (P=0.0482).
The proteoglycan (PG) content of the AF regions of the injured discs was significantly lower than the corresponding region of the non-injured AF disc side as well as the normal controls. In contrast the injured AF regions contained more DNA than the corresponding non-injured AF of the same discs or normal controls. The percentage of PGs extracted from the NP of injured discs was lower than the NP of control discs.
Conclusions: MRI degeneration scores and changes in DHI are consistent with biochemical changes in disc PG content which occur 3 months post annular injury, in a three level ovine model of lumbar disc degeneration.
Patient Care: Biological regenerative therapies, such as stem cell therapies, are likely to play a significant role in the treatment of lumbar disc degeneration in the foreseeable future. In order to determine the efficacy of such therapies prior to their translation into human clinical trials, suitable pre-clinical animal studies are necessary. Methods which reliably and reproducibly induce disc degeneration in animals, and which mimics the human degenerative process, are essential to researchers wanting to investigate such biological therapies.
Learning Objectives: By the conclusion of this session participants should have an understanding of the 3 level ovine annular injury model of lumbar disc degeneration, and the radiological and biochemical changes which occur within the injured discs. The annular injury model is an established model of degeneration however a detailed radiological analysis, including 3T MRI, has not been published to date. This model is similar to human disc degeneration where similar radiological and biochemical changes occur.
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